The Inter-American Human Rights Commission has said that its analysts ran into major setbacks throughout their investigation of the case of 43 university students who went missing in Mexico in 2014. The Commission organized a five-person panel of legal and medical experts to investigate the incident.

Reportedly, the panel has been given only limited access to new information uncovered by the government and criticized the existing statements released by the government from those arrested as being untrue. The commission was also barred from being present while military personnel, who were witnesses at the disappearance, provided statements.

“I’m a doctor – I’m going to use a medical metaphor,” Carlos Beristain, one of the panel’s experts told a news conference. “You could say we are here to strengthen the state’s defenses, a kind of vaccine that we hope stimulates the fight against and resistance to impunity … But for some people, we are a foreign body. If we’re considered less a vaccine that will develop defenses against impunity, and more a foreign body that has to be contained and reacted against, that would be very bad news.”

The Human Rights Commission released its first report this September in which it rejected the official version of events recounted by the government as “historic truth.” Initially, the Mexican government claimed that the students’ bodies were turned over to a local drug gang, which then incinerated the bodies and left them at a dump yard. Soon thereafter, a team of Argentine forensic experts concluded that the bones discovered at the dump did not correspond to the bones of all of the students.

The Human Rights Commission then rejected that official retelling and accused Mexican authorities of tampering with evidence. It convened a five-person panel of experts to probe the incident further. New evidence has emerged that suggests that less than half of the missing students were burned at the dump. Another forensic analysis of the dump is to be conducted before the panel concludes its work.

Jude Webber of the Financial Times reports the panel will terminate on April 30th, giving these experts a little more than two months to conduct the investigation. Critics have suggested the government hopes to run out the clock before further incriminating evidence is uncovered.

The missing students from a local teachers college have not been seen since September 26th, 2014 when they were arrested for clashing with municipal police officers in the city of Iguala in Guerrero state. Six other individuals died during the clashes with local authorities.

The students’ disappearances have sparked a level of outrage unseen in modern Mexican history. In November 2014, protests erupted throughout the country. President Pena Nieto invited heavy criticism for waiting 11 days before issuing a statement about the students’ deaths and waited over seventeen months after the incident before visiting Guerrero state. Many suspect the Mexican government to have been involved in the killing and subsequent coverup of these students’ disappearances.